<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang="en">
<head>
<title>star</title>
<script type="text/javascript">
window.onload = function () {
	C = Math.cos; // cache Math objects
	S = Math.sin;
	U = 0;
	w = window;
	j = document;
	d = j.getElementById("c");
	c = d.getContext("2d");
	W = d.width = w.innerWidth;
	H = d.height = w.innerHeight;//w.innerHeight
	c.fillRect(0, 0, W, H); // resize <canvas> and draw black rect (default)
	c.globalCompositeOperation = "lighter"; // switch to additive color application
	c.lineWidth = 0.2;
	c.lineCap = "round";
	var bool = 0, 
		t = 0; // theta
	d.onmousemove = function (e) {
		if(window.T) {
			if(D==9) { D=Math.random()*15; f(1); }
			clearTimeout(T);
		}
		X = e.pageX; // grab mouse pixel coords
		Y = e.pageY;
		a=0; // previous coord.x
		b=0; // previous coord.y 
		A = X, // original coord.x
		B = Y; // original coord.y
		R=(e.pageX/W * 999>>0)/999;
		r=(e.pageY/H * 999>>0)/999;
		U=e.pageX/H * 360 >>0;
		D=9;
		g = 360 * Math.PI / 180;
		T = setInterval(f = function (e) { // start looping spectrum
			c.save();
			c.globalCompositeOperation = "source-over"; // switch to additive color application
			if(e!=1) {
				c.fillStyle = "rgba(0,0,0,0.02)";
				c.fillRect(0, 0, W, H); // resize <canvas> and draw black rect (default)
			}
			c.restore();
			i = 25; while(i --) {
				c.beginPath();
				if(D > 450 || bool) { // decrease diameter
					if(!bool) { // has hit maximum
						bool = 1;
					}
					if(D < 0.1) { // has hit minimum
						bool = 0;
					}
					t -= g; // decrease theta
					D -= 0.1; // decrease size
				}
				if(!bool) {
					t += g; // increase theta
					D += 0.1; // increase size
				}
				q = (R / r - 1) * t; // create hypotrochoid from current mouse position, and setup variables (see: http://en.wikipedia.org/wiki/Hypotrochoid)
				x = (R - r) * C(t) + D * C(q) + (A + (X - A) * (i / 25)) + (r - R); // center on xy coords
				y = (R - r) * S(t) - D * S(q) + (B + (Y - B) * (i / 25));
				if (a) { // draw once two points are set
					c.moveTo(a, b);
					c.lineTo(x, y)
				}
				c.strokeStyle = "hsla(" + (U % 360) + ",100%,50%,0.75)"; // draw rainbow hypotrochoid
				c.stroke();
				a = x; // set previous coord.x
				b = y; // set previous coord.y
			}
			U -= 0.5; // increment hue
			A = X; // set original coord.x
			B = Y; // set original coord.y
		}, 16);
	}
	j.onkeydown = function(e) { a=b=0; R += 0.05 }
	d.onmousemove({pageX:300, pageY:290})
}

</script>
</head>


<body style="margin:0px;padding:0px;width:100%;height:100%;overflow:hidden;">
<canvas id="c" style="width:100%;height:100%;"></canvas>
</body>
</html>